An aromatic polycarbonate resin has excellent transparency, flame retardancy, heat resistance and strength and is therefore used in a wide variety of fields. However, as electronic and electric equipment parts and OA-related parts are becoming thinner, there is a case where the flame retardancy of the aromatic polycarbonate resin is not satisfactory. In addition, high flame retardancy rated UL (standards of Underwriters Laboratories of the U.S.) 94 V-0 is now often required for the aromatic polycarbonate resin, thereby limiting the application of the aromatic polycarbonate resin. To obtain high flame retardancy, it is important that the dripping of the resin should not occur when it is burnt.
It is known that polytetrafluoroethylene is added to suppress the dripping of the aromatic polycarbonate resin. However, as the secondary agglomeration of polytetrafluoroethylene readily occurs due to the influence of static electricity, when it is mixed with a polycarbonate resin, a feed failure to the cylinder of an extruder is apt to occur. Owing to its dispersion failure, it deteriorates appearance and impact strength. To improve the dispersibility of polytetrafluoroethylene, there are proposed various methods for mixing polytetrafluoroethylene with an organic polymer (refer to Patent Documents 1 to 4).
Meanwhile, design quality including a sensory part is now required for OA-related parts. Although a drip preventing effect is easily obtained when polytetrafluoroethylene is added, transparency lowers. The reduction of transparency degrades light transmittance and causes such inconvenience as the reduction of design width such as coloring including a sensory part. When viewed from the opposite side, it can be said that a material retaining transparency, that is, a material which provides a molded article having low haze (a material having high transparency) has a large design width including a sensory part. Stated more specifically, a transparent color (generally called “skeleton color”) can be given to a material having low haze by using a dye-based colorant, and a translucent color and an opaque color can also be given to the above material by using a pigment-based colorant alone or in combination with the above dye-based colorant. Further, light diffusability can be obtained by adding a light diffusing agent, and a target level of light diffusability can also be provided by controlling the amount of the light diffusing agent. Therefore, the reduction of transparency, that is, the reduction of light transmittance makes it difficult to color a transparent color, thereby reducing the design width associated with coloration including a sensory part and further the provision of light diffusability. Consequently, to expand the design width, satisfactory drip prevention properties must be provided even when the amount of polytetrafluoroethylene is small.
At the same time, excellent hydrolysis resistance is also required to enhance the durabilities of electronic and electric equipment parts and products. To this end, a flame retardant resin composition which has a good appearance due to the improvement of the dispersibility of polytetrafluoroethylene into a resin, high impact resistance, excellent hydrolysis resistance and high drip prevention properties is desired.
Patent Document 1 has a description of the improvement of dispersibility by mixing polytetrafluoroethylene and an organic polymer into a resin but it cannot be said that the disclosed resin composition is satisfactory in terms of hydrolysis resistance. Although the dispersibility of polytetrafluoroethylene is improved by the same method in Patent Documents 2 to 4, it cannot be said that the disclosed resin compositions are satisfactory in terms of hydrolysis resistance and drip prevention properties as well as impact strength. Therefore, it cannot be said that the above prior arts disclose the means of solving the above technical problems completely.
It is known that phosphorus-based, phenol-based and sulfur-based heat stabilizers are effective in the improvement of the heat stability of a polycarbonate resin composition. However, the addition of these heat stabilizers greatly deteriorates hydrolysis resistance.    (Patent Document 1) Japanese Patent No. 3469391    (Patent Document 2) JP-A 2000-297220    (Patent Document 3) Japanese Patent No. 3066012    (Patent Document 4) JP-A 2005-263908